Davis CarChipEX The Davis CarChipEX (and Davis CarChip) can tell you want the 'check engine' light means, and give you the trouble code and a brief description. It can also reset the 'check engine' light." Davis CarChip/CarChipEX: http://www.davisnet.com/drive/products/carchip_products.asp . . . . . If you don't have a serial port connected on your computer (many modern laptops do not have this), you will have to get a USB to serial adapter with the CarChip. Be wary that the standard CarChip only logs vehicle trouble codes (check engine light codes) and speed. The CarChipEX can log vehicle trouble codes (check engine light codes), speed, and 4 out of 23 selectable parameters including RPM; Throttle position ; Engine load ; Fuel pressure ; Fuel system status ; Short- and long-term-fuel trim ; Battery voltage ; Timing advance ; Coolant temperature ; Air flow rate ; Intake air temperature ; Intake manifold pressure ; Oxygen sensor voltage ; The 1999 Subaru Legacy does not log some of these parameters such as i) intake air temperature; ii) Fuel Pressure; only logs 2 of the fuel trim parameters: Short Term Fuel Trim B1 and Long Term Fuel Trim B1; and only 2 of the 8 Oxygen inputs are supported (B1, S1; and B1, S2). National OBD Clearing House at Weber State University.: http://www.autocenter.weber.edu/OBD-CH/vehicleoems.asp Do Your Own Automotive Diagnostics: http://www.davisnet.com/news/press/drive/files/PC_Toys_Chpt_9.PDF

Images showing where to find the place the OBDII connector in a 1999 Subaru Legacy The National OBD Clearing House at Weber State University at http://www.autocenter.weber.edu/OBD-CH/vehicleoems.asp lists where the connectors are in the various car models available. . . . .

Example Log Plots generated by Davis CarChipEX (this is supported by Standard CarChip, except speed vs time plots) . . Car Speed; Short Term Fuel Trim; Long Term Fuel Trim . . . Car Speed; Fuel System Status; Air Flow Rates (kg/s); Engine Speed (RPM) . . . . Car Speed; Coolant Temperature; Short Term Fuel Trim; Battery Voltage . . Car Speed; Oxygen Sensor B1, S1; Oxygen Sensor B1, S2

What a Trouble Code can look like View / Vehicle Trouble Log / Summary Time Vehicle Trouble Code Description Problem 1 19/02/2004 16:43 Mel's Honda P1491 Unknown Powertrain DTC (Manufacturer Controlled; Auxiliary Emission Controls) Details of the Trouble Code View / Vehicle Trouble Log / Record Problem 1 Overview Time : 19/02/2004 16:43 Vehicle : Mel's Honda CarChip : J-9889-A Trouble Code : P1491 Description : Unknown Powertrain DTC (Manufacturer Controlled; Auxiliary Emission Controls) Comments : Engine Status Fuel Pressure (Gage) : Intake Manifold Pressure (Absolute) : 51 kPa Engine Coolant Temperature : 46.00 °C Calculated Load Value : 50.6 % Engine Speed : 1,764 RPM Vehicle Speed : 78 kph Fuel Trim Status Short-Term Fuel Trim (Bank 1) : 13.28 % Short-Term Fuel Trim (Bank 2) : Long-Term Fuel Trim (Bank 1) : 0.00 % Long-Term Fuel Trim (Bank 2) : Fuel System Status Fuel System 1 Status : Fuel System 2 Status : Closed loop; using oxygen sensor(s) as feedback for fuel control. Correlating the trouble code with loggable data from a Davis CarChipEX In the above case, systematically going through the loggable data shows the Long Term Fuel trim seems to always be at 0.00 %. (logging of Short-Term Fuel Trim (Bank 2) and Long-Term Fuel Trim (Bank 2) are not supported by the vehicle) View / Trip Log / Record Trip 2 Vehicle : Mel's Honda CarChip : J-9889-A Start Time : 19/02/2004 16:42 End Time : 19/02/2004 16:56 Duration : 00:14:31 Idle : 00:00:00 0 to 72 kph : 00:05:02 72 to 97 kph : 00:07:55 97 to 121 kph : 00:01:34 Over 121 kph : 00:00:00 Distance : 18.2 km Average Speed : 75 kph Maximum Speed : 107 kph Hard Brakes : 1 (Between 0.28 G and 0.48 G) Extreme Brakes : 0 (Over 0.48 G) Hard Accelerations : 0 (Between 0.28 G and 0.48 G) Extreme Accelerations : 0 (Over 0.48 G) Parameters Parameter 1 : Vehicle Speed Every 5 Seconds Parameter 2 : Short Term Fuel Trim (B1) Every 5 Seconds Parameter 3 : Short Term Fuel Trim (B2) Every 5 Seconds (Not Supported By Vehicle) Parameter 4 : Long Term Fuel Trim (B1) Every 5 Seconds Parameter 5 : Long Term Fuel Trim (B2) Every 5 Seconds (Not Supported By Vehicle) Comments : . .